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Isoamylase (Glycogen 6-glucanohydrolase)

Product code: E-ISAMY
€220.00

600 Units

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Content: 600 Units
Shipping Temperature: Ambient
Storage Temperature: 2-8oC
Formulation: In 3.2 M ammonium sulphate
Physical Form: Suspension
Stability: > 4 years at 4oC
Enzyme Activity: Isoamylase
EC Number: 3.2.1.68
CAZy Family: GH13
CAS Number: 9067-73-6
Synonyms: isoamylase; glycogen 6-alpha-D-glucanohydrolase
Source: Pseudomonas sp.
Molecular Weight: 71,500
Concentration: Supplied at ~ 200 U/mL
Expression: Purified from Pseudomonas sp.
Specificity: Hydrolysis of (1,6)-α-D-glucosidic branch linkages in glycogen, amylopectin and their β-limit dextrins.
Specific Activity: ~ 180 U/mg (40oC, pH 4.0 on oyster glycogen) (equivalent to 16 MU Sigma Units/mg)
Unit Definition: One unit of isoamylase activity is the amount of enzyme required to release one µmole of D-glucose reducing sugar equivalent in the presence of oyster glycogen per min at pH 4.0 and 40oC.
Temperature Optima: 50oC
pH Optima: 4
Application examples: Applications in carbohydrate research and in the food and feeds, and cereals industry.
Method recognition: AOAC Method 2000.11 and GB Standard 5009.245-2016

Pure Isoamylase (Glycogen 6-glucanohydrolase) for use in biochemical enzyme assays and in vitro diagnostic analysis. Isoamylase, Fructanase (E-FRMXPD) and Amyloglucosidase (E-AMGDF) are used in the enzyme hydrolysis step of two validated methods for the determination of polydextrose (a low molar mass dietary fiber) in foods: AOAC method 2000.11 and Chinese GB Standard 5009.245-2016.

Please refer to E-ISAMYHP for high purity enzyme suitable for use in starch structural research.

We have a wide range of other CAZyme products available.

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Publications
Publication

The Physicochemical Properties of Starch Are Affected by Wxlv in Indica Rice.

Feng, L., Lu, C., Yang, Y., Lu, Y., Li, Q., Huang, L., Fan, X., Liu, Q. & Zhang, C. (2021). Foods, 10(12), 3089.

Amylose largely determines rice grain quality profiles. The process of rice amylose biosynthesis is mainly driven by the waxy (Wx) gene, which also affects the diversity of amylose content. The present study assessed the grain quality profiles, starch fine structure, and crystallinity characteristics of the near-isogenic lines Q11(Wxlv), NIL(Wxa), and NIL(Wxb) in the indica rice Q11 background containing different Wx alleles. Q11(Wxlv) rice contained a relatively higher amylose level but very soft gel consistency and low starch viscosity, compared with rice lines carrying Wxa and Wxb. In addition, starch fine structure analysis revealed a remarkable decrease in the relative area ratio of the short amylopectin fraction but an increased amylose fraction in Q11(Wxlv) rice. Chain length distribution analysis showed that Q11(Wxlv) rice contained less amylopectin short chains but more intermediate chains, which decreased the crystallinity and lamellar peak intensity, compared with those of NIL(Wxa) and NIL(Wxb) rice. Additionally, the starches in developing grains showed different accumulation profiles among the three rice lines. Moreover, significant differences in starch gelatinization and retrogradation characteristics were observed between near-isogenic lines, which were caused by variation in starch fine structure. These findings revealed the effects of Wxlv on rice grain quality and the fine structure of starch in indica rice.

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Publication

Structural properties of starch from single kernel of high-amylose maize.

Lin, L., Zhao, S., Li, E., Guo, D. & Wei, C. (2021). Food Hydrocolloids, 124, 107349.

Cereal grain weight is an important agronomic character, influencing crop yield and quality. The high-amylose cereals usually have grains with different weights. However, it is unclear whether starches from kernels with different weights have different structural properties. In the research, the amylose content, amylopectin structure, crystallinity, and thermal properties of single-kernel starch were investigated in two high-amylose maize inbred lines, and the relationship between amylose/amylopectin content and kernel weight and the differences of starches from kernels with different weights were analyzed. The results showed that kernel weight had significantly positive relationship with amylose content and amylopectin B3+ chains (DP > 36) and average branch-chain length and negative relationship with amylopectin A chains (DP6-12) and B1 chains (DP13-24). The amylopectin A and B1 chains, relative crystallinity, and ordered degree had positive relationship with each other. The amylose content, amylopectin B3+ chains and average branch-chain length, and gelatinization temperature range were positively correlated with each other. Starches from kernels with different weights had different amylose contents, amylopectin structures, and thermal properties. The above results would offer references for breeding of high-amylose cereal crops and applications of grains with different weights.

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Publication

Maltogenic α-amylase hydrolysis of wheat starch granules: mechanism and relation to starch retrogradation.

Zhai, Y., Li, X., Bai, Y., Jin, Z. & Svensson, B. (2021). Food Hydrocolloids, 124, 107256.

Enzymatic modification is an effective method to inhibit starch retrogradation. However, lack of quantification of relationships between enzymatic modification and starch retrogradation makes the enzymatic improvement unpredictable. In this study, maltogenic α-amylase (MA) was used to treat wheat starch granules to restrain retrogradation, aiming to elucidate the mechanism of MA hydrolysis on wheat starch granules and to establish a quantitative relationship between the degree of hydrolysis (DH) and retrogradation. Scanning electron microscopy and small angle X-ray scattering results showed that MA hydrolyzed starch granules by a “surface pitting” mode simultaneously acting on crystalline and amorphous regions. Debranching and high performance anion exchange chromatography analysis of MA-treated wheat starch granules demonstrated that the amount of short branches with degree of polymerization<9 increased and the proportion of medium and long branches decreased. Importantly, the extent of impaired short- and long-term retrogradation of MA-treated starch was clearly linearly correlated with the DH. This finding provides a quantitative method for predicting the degree of retrogradation improvement by enzymatic modification.

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Publication

Development of freeze-Thaw stable starch through enzymatic modification.

Woo, S. H., Kim, J. S., Jeong, H. M., Shin, Y. J., Hong, J. S., Choi, H. D. & Shim, J. H. (2021). Foods, 10(10), 2269.

The use of unmodified starch in frozen foods can cause extremely undesirable textural changes after the freeze-thaw process. In this study, using cyclodextrin glucanotransferase (CGTase) and branching enzymes, an amylopectin cluster with high freeze-thaw stability was produced, and was named CBAC. It was found to have a water solubility seven times higher, and a molecular weight 77 times lower, than corn starch. According to the results of a differential scanning calorimetry (DSC) analysis, dough containing 5% CBAC lost 19% less water than a control dough after three freeze-thaw cycles. During storage for 7 days at 4°C, bread produced using CBAC-treated dough exhibited a 14% smaller retrogradation peak and 37% less hardness than a control dough, suggesting that CBAC could be a potential candidate for clean label starch, providing high-level food stability under repeated freeze-thaw conditions.

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Publication

Slowly digestible property of highly branched α-limit dextrins produced by 4, 6-α-glucanotransferase from Streptococcus thermophilus evaluated in vitro and in vivo.

Ryu, J. J., Li, X., Lee, E. S., Li, D. & Lee, B. H. (2021). Carbohydrate Polymers, 275, 118685.

Starch molecules are first degraded to slowly digestible α-limit dextrins (α-LDx) and rapidly hydrolyzable linear malto-oligosaccharides (LMOs) by salivary and pancreatic α-amylases. In this study, we designed a slowly digestible highly branched α-LDx with maximized α-1,6 linkages using 4,6-α-glucanotransferase (4,6-αGT), which creates a short length of α-1,4 side chains with increasing branching points. The results showed that a short length of external chains mainly composed of 1–8 glucosyl units was newly synthesized in different amylose contents of corn starches, and the α-1,6 linkage ratio of branched α-LDx after the chromatographical purification was significantly increased from 4.6% to 22.1%. Both in vitro and in vivo studies confirmed that enzymatically modified α-LDx had improved slowly digestible properties and extended glycemic responses. Therefore, 4,6-αGT treatment enhanced the slowly digestible properties of highly branched α-LDx and promises usefulness as a functional ingredient to attenuate postprandial glucose homeostasis.

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Publication

Corn starch modification during endogenous malt amylases: The impact of synergistic hydrolysis time of α-amylase and β-amylase and limit dextrinase.

Gui, Y., Zou, F., Li, J., Tang, J., Guo, L. & Cui, B. (2021). International Journal of Biological Macromolecules, 190, 819-826.

To expand the utility of barley malts and decrease the cost of enzyme-modified starch production, the structural and physicochemical characteristics of corn starch modified with fresh barley malts at different hydrolysis time were investigated. The results indicated that compared to native starch, A chain (DP 6-12) of the enzyme-treated starches increased at hydrolysis time (≤12 h), but it decreased at hydrolysis time (>12 h). Inversely, B chains (DP > 13) decreased at hydrolysis time (≤12 h) and they generally increased at hydrolysis time (>12 h). The relative crystallinity decreased from 25.63% to 21.38% and 1047 cm−1/1022 cm−1 reduced from 1.042 to 0.942 after endogenous malt amylases at hydrolysis time from 0 to 72 h, and the thermal degradation temperatures decreased from 323.19 to 295.94°C, whereas the gelatinization temperatures slightly increased. The gel strength decreased at hydrolysis time less than 12 h, but it increased at hydrolysis time more than 12 h. The outcomings would provide a theoretical and applicative basis about how endogenous malt amylases with lower price modify starches to obtain desirable starch derivatives and industrial production.

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Publication

Ethanol pretreatment increases the efficiency of maltogenic α-amylase and branching enzyme to modify the structure of granular native maize starch.

Zhong, Y., Herburger, K., Xu, J., Kirkensgaard, J. J. K., Khakimov, B., Hansen, A. R. & Blennow, A. (2022). Food Hydrocolloids, 123, 107118.

A method for efficient functional modification of starch granules by thermal ethanol pre-treatment and subsequent maltogenic α-amylase (MA) and branching enzyme (BE) post-treatments is described. Ethanol pre-treatment significantly increased the swelling power of starch granules thereby increasing the MA and BE susceptibility. Ethanol pre-treated granules became shrunk and twisted after incubating in buffer. Sequential MA post-treatments remarkably increased the α-1,6 to α-1,4 ratio and the content of amylopectin short chains (DP 1-10), contributing to the low retrogradation rate. BE post-treatments significantly decreased the product yield, increased the relative crystallinity of starch granules, suggesting BE had intramolecular transglucosylation activity which altered the branch position and reduced the molecular size by forming cyclic structures. Moreover, BE post-treatments showed an α-1,6 to α-1,4 transglucosylation activity by decreasing the α-1,6 to α-1,4 ratio, especially during simultaneous MA and BE catalysis. However, in the simultaneous MA and BE post-catalysis, MA dosage was predominant by noticeably hydrolyzing amylopectin and amylose molecules and increasing the α-1,6 to α-1,4 ratio, thereby leading to the lowest digestibility and retrogradation.

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Publication

Enzymatic modification of potato starch by amylosucrase according to reaction temperature: Effect of branch-chain length on structural, physicochemical, and digestive properties.

Jung, D. H., Park, C. S., Kim, H. S., Nam, T. G., Lee, B. H., Baik, M. Y., Yoo, S. & Seo, D. H. (2022). Food Hydrocolloids, 122, 107086.

Branch-chain elongated starches can be synthesized by amylosucrase (AS). In this study, potato starches with different branch-chain length were produced using the temperature-dependent elongation property of AS from Deinococcus geothermalis (DGAS). Decreasing the reaction temperature led to a significant rise in the length of the branch-chains, in addition to amylose content. As branch-chain length increased, B-type crystal structure increased significantly alongside it, and the thermal transitions were enhanced, suggesting that the crystalline structure was further stabilized. In addition, a decrease in solubility and swelling power was observed, whereas the gelatinization temperatures and peak viscosities increased accordingly. With respect to digestive properties, a remarkable rise in slowly digestible starch (0-19.8%) and resistant starch (38.2%-62.2%) contents was observed, along with an enhanced resistance to mammalian mucosal α-glucosidase. In conclusion, enzymatic modification by DGAS might be an innovative method to regulate the physicochemical and digestive properties of starches.

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Publication

The combined effects of extrusion and recrystallization treatments on the structural and physicochemical properties and digestibility of corn and potato starch.

Liu, Q., Jiao, A., Yang, Y., Wang, Y., Li, J., Xu, E., Yang, G. & Jin, Z. (2021). LWT, 151, 112238.

This study aimed to compare the effects of extrusion and recrystallization treatments on the structural and physicochemical properties and digestibility of corn (CS) and potato starch (PS). CS and PS were conditioned at 40 % and 60 % moisture content and extruded at 40°C-120°C. The extrudates were stored for 1, 7, and 14 days at 4°C for recrystallization. The structural properties of extruded CS (ECS) and extruded PS (EPS), as well as the crystallization and thermal properties, water solubility, water absorption, and in vitro digestibility of recrystallized ECS (RECS) and recrystallized EPS (REPS), were evaluated. Compared with native starch, both ECS and EPS exhibited a significant decrease in their measured molecular weight. The chain length distribution did not change significantly, but the amylose content increased remarkably. Both RECS and REPS with 60 % moisture content presented a typical B-type pattern, and RECS exhibited V-type characteristic peaks. The melting signals of recrystallized amylopectin (46-64°C) and amylose (136-158°C) of RECS were detected. In vitro digestion experiments showed that RECS had lower digestibility than REPS. The highest slowly digestible starch and resistant starch contents of RECS were approximately 3.5 and 6.5 times that of unextruded CS, respectively.

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Publication

The effects of molecular fine structure on rice starch granule gelatinization dynamics as investigated by in situ small-angle X-ray scattering.

Xu, J., Li, Z., Zhong, Y., Zhou, Q., Lv, Q., Chen, L., Blennow, A. & Liu, X. (2021). Food Hydrocolloids, 121, 107014.

Dynamic changes of rice starch granules selected for different amylose contents were analyzed in excess water while heated in-situ in a small-angle X-ray scattering (SAXS) instrument. Normal rice starch (NS) and rice starch with high amylopectin (HAP) and high amylose (HAM) were used as models. A 1D linear correlation function and a combination power-law and Gaussian function were used to extract the starch lamellar structure parameters and the fractal dimension, ordering and distribution of starch lamellae from SAXS data. For the resulting starch paste/gels, a model of two-correlation length was fitted to afford the correlation length (ξ) for the paste/gel system. The results showed that HAM exhibited higher long period (LP) and thickness of the crystalline layers (dc) values than HAP and NS. However, HAP showed the highest ordering lamellar structure. HAP granules were more thermostable than the amylose containing starches. For the gelatinized starches, HAM showed the highest correlation length values but these notably decreased with increasing temperature indicating strong chain segment interaction. This research reveals essential structural changes in lamellae of rice starch granules and rice starch gel structure, which provides potentially useful in the working of starch-based foods and materials.

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Salt Tolerance at Vegetative Stage is Partially Associated with Changes in Grain Quality and Starch Physicochemical Properties of Rice Exposed to Salinity Stress at Reproductive Stage.

Sangwongchai, W., Krusong, K. & Thitisaksakul, M. (2021). Journal of the Science of Food and Agriculture, In Press.

Background: Rice yield and grain quality are highly sensitive to soil salinity. Distinct rice genotypes respond to salinity stress differently. To explore the variation in grain yield and grain trait adaptation to moderate, reproductive-stage salinity stress (4 dS/m electrical conductivity), four rice cultivars differing in degrees of vegetative salt tolerance, including Pokkali (salt-tolerant), RD15 (moderately salt-tolerant), KDML105 (moderately salt-susceptible) and IR29 (salt-susceptible), were examined. Results: Grain fertility and 100-grain weight of RD15, KDML105 and IR29, as well as grain morphology of KDML105 and IR29, were significantly disturbed. Interestingly, grain starch accumulation in RD15 and KDML105 was enhanced under stress. However, only RD15 showed changes in starch physicochemical properties, including increased granule diameter, decreased gelatinization peak temperature (Tp) and decreased retrogradation onset temperature (To). Notably, Pokkali maintained productivity, grain quality, and starch properties, while the grain quality of IR29 remained unchanged under salinity stress. Multivariate analysis displayed clear separation of productivity, grain morphology, and starch variables of RD15 in the salt-treated group relative to the control group, suggesting that it was the cultivar most impacted by salt stress despite its moderate salt-tolerance at vegetative stage. Conclusion: Our results demonstrate specific salinity responses among the rice genotypes, and suggest discrepancies between degrees of salt tolerance at vegetative stage versus the ability to maintain both grain quality and starch properties in response to salinity stress imposed at reproductive stage.

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Publication

Sequential maltogenic α-amylase and branching enzyme treatment to modify granular corn starch.

Zhong, Y., Herburger, K., Kirkensgaard, J. J. K., Khakimov, B., Hansen, A. R. & Blennow, A. (2021). Food Hydrocolloids, 120, 106904.

Due to the semi-crystalline structure of native starch granules, enzymatic modification of these solid, raw, entities by branching enzyme (BE) is limited. Here, we describe a method to efficiently modify starch by BE after maltogenic α-amylases pre-treatment. This pre-treatment produced pores at the starch granule surface, which decreased the granular yield, but increased the branching degree in starch molecules. BE post-treatments recovered the yield, increased the content of long amylose chains, and the starch crystallinity. WAXS analysis showed that BE transformed the unresolved doublet peak at 2θ 17° and 18° to a strong peak at 2θ 17°, i.e. transformed the granules from the A-type to a mixed A-, B-type allomorph. Syneresis of starch gels increased with increasing BE concentrations and increased the content of slowly digested starch in retrograded starch preparations. Rheology data demonstrated that low and medium BE concentrations produced starch gels with higher G′ and G″ after storage for 1day, whereas high BE concentrations reduced both G′ and G’’. Our data demonstrate the potential of clean, enzyme-based protocols using sequential addition of starch active enzymes for post-harvest modification of raw starch granules to obtain clean and functional starch.

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Publication

Structural elements determining the transglycosylating activity of glycoside hydrolase family 57 glycogen branching enzymes.

Xiang, G., Leemhuis, H. & van der Maarel, M. (2021). Authorea Preprints, In Press.

Glycoside hydrolase family 57 glycogen branching enzymes (GH57GBE) catalyze the formation of an α-1,6 glycosidic bond between α-1,4 linked glucooliogosaccharides. As an atypical family, a limited number of GH57GBEs have been biochemically characterized so far. This study aimed at acquiring a better understanding of the GH57GBE family by a systematic sequence-based bioinformatics analysis of almost 2500 gene sequences and determining the branching activity of several native and mutant GH57GBEs. A correlation was found in a very low or even no branching activity with the absence of a flexible loop, a tyrosine at the loop tip, and two β-strands.

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Influence of microwave treatment on the structure and functionality of pure amylose and amylopectin systems.

Zhong, Y., Tian, Y., Liu, X., Ding, L., Kirkensgaard, J. J. K., Hebelstrup, K., Putaux, J. L. & Blennow, A. (2021). Food Hydrocolloids, 119, 106856.

Pure granular amylose (AM) and pure granular amylopectin (waxy) starch (AP) granules have the high nutritional value in food industry. Effects of microwave treatment (400 W/g DW, 1-8 min) on the structure and properties of transgenic AM granules and AP granules were investigated in direct comparison. Microwave treatment, especially during the first 3 min, decreased the molecular weight of molecules in both the AM and the AP samples. The crystallinity of AM starch initially increased from 15.6% to 20.6%, which was associated with the formation of new Vh-type crystals. After that, crystallinity decreased alongside to 11.3% with the complete disruption of B-type crystals. In contrast, the crystallinity of AP starch initially decreased from 18.9% to 10.8% followed by an increase to 20.0%. Upon prolonged treatment of AM granules, the resistant starch and water solubility was significantly increased. Our data demonstrate notable different microwave-dependent reorganization patterns for pure granular AM and AP molecules as native granular systems, which is helpful to the improvement of functionality of these two starches.

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Supermolecular structures of recrystallized starches with amylopectin side chains modified by amylosucrase to different chain lengths.

Zhang, H., Qian, S., Rao, Z., Chen, Z., Zhong, Q. & Wang, R. (2021). Food Hydrocolloids, 119, 106830.

Understanding the supermolecular structures of recrystallized starches is imperative to manufacture novel starches with controllable physicochemical properties enabling novel applications. In this study, native amylopectin (AP) from maize was modified to different chain lengths using amylosucrase from Neisseria polysaccharea. Native AP granules showed well-organized lamellar structures with a periodicity of ca. 9.0 nm whereas modified starches formed heterogeneous structures with the average crystallite size ranging from 19.77 to 29.88 nm. Acidic treatments eroded amorphous domains in both native AP granules and modified starch particles, producing nanocrystals composed of double helices. A-type nanocrystals (~40 nm) from native AP granules showed quadrangular shape with an acute angle of ca. 60 , while irregular B-type nanocrystals were observed for the modified starches. Molecular characterizations suggested that the nanocrystals had relatively uniform chain lengths (DP 16.5-25.2), and the helix length (the thickness of nanocrystals) was positively correlated to the thermal stability of starches.

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Digestibility of resistant starch type 3 is affected by crystal type, molecular weight and molecular weight distribution.

Klostermann, C. E., Buwalda, P. L., Leemhuis, H., de Vos, P., Schols, H. A. & Bitter, J. H. (2021). Carbohydrate Polymers, 265, 118069.

Resistant starch type 3 (RS-3) holds great potential as a prebiotic by supporting gut microbiota following intestinal digestion. However the factors influencing the digestibility of RS-3 are largely unknown. This research aims to reveal how crystal type and molecular weight (distribution) of RS-3 influence its resistance. Narrow and polydisperse α-glucans of degree of polymerization (DP) 14-76, either obtained by enzymatic synthesis or debranching amylopectins from different sources, were crystallized in 12 different A- or B-type crystals and in vitro digested. Crystal type had the largest influence on resistance to digestion (A >>> B), followed by molecular weight (Mw) (high DP >> low DP) and Mw distribution (narrow disperse > polydisperse). B-type crystals escaping digestion changed in Mw and Mw distribution compared to that in the original B-type crystals, whereas A-type crystals were unchanged. This indicates that pancreatic α-amylase binds and acts differently to A- or B-type RS-3 crystals.

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Dataset on viscosity and starch polymer properties to predict texture through modeling. Buenafe, R. J. Q., Kumanduri, V. & Sreenivasulu, N. (2021). Data in Brief, 36, 107038.

Dataset on viscosity and starch polymer properties to predict texture through modeling. Buenafe, R. J. Q., Kumanduri, V. & Sreenivasulu, N. (2021). Data in Brief, 36, 107038.

Accurate classification tool for screening varieties with superior eating and cooking quality based on its pasting and starch structure properties is in demand to satisfy both consumers’ and farmers’ need. Here we showed the data related to the article entitled “Deploying viscosity and starch polymer properties to predict cooking and eating quality models: a novel breeding tool to predict texture” which provides solution to this problem. The paper compiles all the pasting, starch structure, sensory and routine quality data of the rice sample used in the article into graphical form. It also shows how the data were processed and obtained.

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The role of indica starch in the mechanism of formation of fresh rice noodles.

Yi, C., Zhu, H., Zhang, Y., Wu, S. & Bao, J. (2021). Journal of Cereal Science, 99, 103212.

Starch is the largest component in frequently consumed fresh rice noodles (FRN). The effects of morphology, relative crystallinity, molecular weight distribution and physicochemical (rheological, water hydration and gel texture) properties of starch from five rice cultivars with different amylose contents on the formation of FRN were investigated. FRN made from NR rice cultivar, used for commercial rice noodles making, showed excellent FRN texture. NR starch exhibited larger G′ and smaller tan δ values. The morphology of FRN from GM03 cultivar was closest to NR, but had higher hardness and lower springiness, resilience and cohesiveness. Its starch granules morphology was relatively small and round. The extracted starch from Zhongzao 35, Zao 87 and BX02 rice cultivars, with higher swelling power or lower proportions of amylose (FrI) and higher proportions of amylopectin (FrII), could not produce a dense and consistent FRN structure. It was observed that relative crystallinity of the starch samples had no influence on the formation of FRN. Nevertheless, the gel texture of starch played a role in the formation of FRN. The formation of FRN is the common effect of structure and physicochemical properties of rice starch. The finding of this research would be useful in understanding the role of starch in producing FRN of high quality.

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Influence of physicochemical properties and starch fine structure on the eating quality of hybrid rice with similar apparent amylose content.

Peng, Y., Mao, B., Zhang, C., Shao, Y., Wu, T., Hu, L., Hu, Y., Li, Y., Tang, W., Xiao, W. & Zhao, B. (2021). Food Chemistry, 353, 129461.

In this study, we compared the physicochemical properties and starch structures of hybrid rice varieties with similar apparent amylose content but different taste values. In addition to the apparent amylose content, gel permeation chromatography analysis showed that the higher proportions of amylopectin short chains and relatively lower proportions of amylopectin long chains, which could lead to higher peak viscosity and breakdown value, as well as a softer and stickier texture of cooked rice, were the key factors in determining the eating quality of hybrid rice. High-performance anion-exchange chromatography analyses showed that the proportion of amylopectin short chains (degree of polymerization 6-10) and intermediate chains (degree of polymerization 13-24), which might affect the gelatinisation enthalpy and crystallinity, also contributed greatly to the eating quality of hybrid rice. Moreover, this study indicated that a greater diversity of forms and sizes of starch granules might influence the eating quality of hybrid rice.

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Conservation of the glycogen metabolism pathway underlines a pivotal function of storage polysaccharides in Chlamydiae.

Colpaert, M., Kadouche, D., Ducatez, M., Pillonel, T., Kebbi-Beghdadi, C., Cenci, U., Huang, B., Chabi, M., Maes, E., Coddeville, B., Couderc, L., Touzet, H., Bray, F., Tirtiaux, C., Ball, S., Greub, G. & Colleoni, C. (2021). Communications Biology, 4(1), 1-16.

The order Chlamydiales includes obligate intracellular pathogens capable of infecting mammals, fishes and amoeba. Unlike other intracellular bacteria for which intracellular adaptation led to the loss of glycogen metabolism pathway, all chlamydial families maintained the nucleotide-sugar dependent glycogen metabolism pathway i.e. the GlgC-pathway with the notable exception of both Criblamydiaceae and Waddliaceae families. Through detailed genome analysis and biochemical investigations, we have shown that genome rearrangement events have resulted in a defective GlgC-pathway and more importantly we have evidenced a distinct trehalose-dependent GlgE-pathway in both Criblamydiaceae and Waddliaceae families. Altogether, this study strongly indicates that the glycogen metabolism is retained in all Chlamydiales without exception, highlighting the pivotal function of storage polysaccharides, which has been underestimated to date. We propose that glycogen degradation is a mandatory process for fueling essential metabolic pathways that ensure the survival and virulence of extracellular forms i.e. elementary bodies of Chlamydiales.

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